The present invention relates to an image processing method and apparatus, and more particularly to an image rotation method and an image rotation processing apparatus which can perform high-speed real-time processing.
Recently introduced computer image processing systems carry out image processing functions such as reduction or enlargement of an image, rotation, etc. Since the system needs to process a great deal of information at a high speed, a high-priced, special operation processing circuit is provided pertaining to each field. Accordingly, in a general personal computer which is not provided with the special operation processing circuit, image processing such as reduction, enlargement, rotation, etc. depends on software, so that the processing speed is slow and the real-time processing is difficult.
For example, when the image rotation method displays an image on an X-Y plane, and the coordinates of the present position of the image element are denoted (x,y), the coordinates of the resulting position of the image element after rotation through a specified angle .theta. are denoted (x',y'). These post-rotational image element coordinates (x',y') are easily obtained according to image transformation relations including the following matrix relations.
The matrix relations are as follows. ##EQU1##
From the above matrix relations (1), the coordinate of the X-axis (herein denoted x') and the coordinate of the Y-axis (herein denoted y') of the image element coordinates (x', y') after rotational transformation are obtained easily. ##EQU2##
Here, if the sine value ( sin .theta.) and the cosine value ( cos .theta.) of the rotational displacement resulting from rotation through the stated specified angle .theta. are denoted as first and second rotational displacement data (m, n) respectively, the relations (2) may be changed to the following relations (3). ##EQU3##
Therefore, if the X-axis point (herein x) and the Y-axis point (herein y) of the coordinates of the image element (x,y) before rotation are known, the coordinates (x',y') of the new position can be obtained by four multiplication operations, based on the relations (3).
Thus, since the conventional method requires the four multiplication operations when the image rotates, a floating point multiplier is needed for the image rotation processing hardware. The image processing system of a general personal computer without such hardware processes the multiplication through software, but requires such a long time to do the four multiplication operations of the rotation, that real-time processing is difficult.